Structural Radar Imaging’s ground
penetrating radar glossary

Antenna separation – Spacing between transmitting and receiving antennas.

Attenuation – A measure of the loss of radiated signal amplitude or signal energy as it progresses through a loss medium. The loss can be due to a spreading loss as the wave expands out into the medium and also due to an ohm loss, due to the finite conductivity of the medium.

Bandwidth – The range of frequencies over which a given device transmits or detects signals above a specified amplitude or power

Clutter – Unwanted reflections from the ground, from within the ground or from above the ground. In the case of ground penetrating radar (GPR), clutter may be produced by boulders, soil interfaces and other scatterers that are not of interest. Clutter is also produced within the radar system.

CMP – common mid-point (survey type where transmitter and receiver antenna separations are changed but the mid point remains constant)

Control Unit – An electronic instrument that interfaces a transducer (s) to recorders, processors, displays, survey wheel, power supply, etc. It also has controls to allow radar functions such as range, gain and filtering to be adjusted. A C/U can be analog, digital, or hybrid.

COR – common offset reflection (survey type where a constant antenna separation is maintained).

Cross section – Image that results from side-by-side display of a number of traces which are from adjacent spatial measurement position

Depth of Penetration – In any medium, the radar wave is attenuated as it progresses due to losses that occur. At radar frequencies in a conductive material (sea water, metallic materials, clay soils, etc.) the rate of attenuation is very great and the wave may penetrate only a short distance (<1m) before being reduced to a negligibly small value. In a resistive dielectric earth material (fresh water, granite, quartz sand, etc.), where the losses are low, the depth of penetration can be quite great (>30m).

Echoes – Radar energy reflected from a given target or object.

Electromagnetic radiation – a self propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other.

Geophysical Investigation – use of multiple survey techniques in a cost efficient manner to gain maximum information on sub-surface archaeological structures.

Ground penetrating radar – a system that uses radar to locate utilities beneath the surface of the earth, in or below cement, or in or below other non-conductive materials.

GPR – ground penetrating radar

Nodig or no-dig – is a term often used for inspection techniques where digging is not necessary, such as survey methods using GPR, or ground penetrating radar.

Non-destructive testing – examining the interior of products for voids and defects without damaging the outer shell or surface.

Reflection – The degree to which an object returns incident radio waves.

Resolution – The ability to separate two features that are very close together. The minimum separation of two bodies before their individual identities is impossible to interpret. The smallest change in input that will produce a detectable change in output.

Scatter – The irregular and diffuse dispersion of energy caused by imhomogeneities in the medium through which the energy is traveling.

Station interval – Spatial distance between observation points along a survey traverse line or mesh points on a grid.

Transducer – Name used where GPR antenna, electronics, and shield are combined into one physical unit

Transmitter – The electronics, which after receiving a trigger pulse from the control unit, sends an impulse of electromagnetic energy to the attached antenna.

Vertical Resolution – The ability to separate two feature within one scan that are very close together. The minimum separation of two bodies before their individual identities is lost on the resultant map or cross-section. A function of transducer frequency, sampling interval and range.